Multicylinder free piston machine



Dec. 20, 1949 E. MERCIER MULTICYLINDER FREE PISTON MACHINE Filed April 28. 1945 EYrlesT Merczr qPatented Dec. 20, 1949 2,491,679 MULTICYLINDER FREE PISTON MACHINE Ernest Mercier, Paris, France, assignor, by menne assignments, to Moore,

corporation of Georgia Application April 28, i945, Serial No. 590.918 In France February 11, 1941 Claims. i

This invention relates to power developing and to power utilizing machines in which a plurality oi cylinders having pistons reciprocable therein cperateto develop or to utilize the power. The invention particularly relates to machines of this type in which a pair of so-called free pistons or twin pistons and their cooperating cylinders are arranged in aligned relation to each other, it being a purpose of the invention to provide for increase in the power developed or applied in the cycle of operation, for compactness of the apparatus. increased safety and other advantages including those of multi-cycle operation. The machines of the invention may be constructed as internal combustion engines or as air compressors.

in the use oi tree-piston or twin-piston machines it is advantageous to couple two or more prime movers with a phase difference of one stroke in order to obtain a power impulse for each stroke. When this is done regenerators or air cushions intended to return the driving pistons toward the centre during their compression strokes can be dispensed with.

Such arrangements can be realized, for instance, by the tandem coupling of a pair of freepiston engines in line with each other s0 that Y the driving stroke in the one takes place at the same time as the compression stroke is periormed in the other. The outer pistons of these two engines are connected rigidly as are also the inner pistons thereof. This arrangement has the clisadvantage of increasing the length of the machine substantially.

This invention has for one of its objects the provision of a multicylinder free-piston machine comprising a number of free-piston prime movers and a number of free-piston compressors, all oi' which have their axes parallel and distributed about one central axis parallel to said cylinder axes. The invention is characterized particularly in the feature that the elementary machines are divided into two groups and that all the machines in either group operate in synchronism, those pertaining to one group being out of phase by one stroke with respect to those belonging to the other group.

Various embodiments of this` invention are shown in the drawings by way of example but the invention is not intended to be limited to these embodiments.

Figures l and 2 show one embodiment of the invention, Fig. 1 being a longitudinal section on line l-i of Fig. 2 and Fig. 2 a cross-sectional view on line t-i of Fig. l.

Inc., Atlanta, Ga., a

metrically about a central axis on a circle located' in a plane at right angles to the central axis and to the common direction of the axes of the various twin-piston prime movers or motors to be interconnected. Where the driving cylinders 'have al1 the same diameter (which is not absolutely necessary as a principle), there must be an even number of them. The motors may be considered as distributed by pairs in two groups. The pistons in one group are out of phase by one stroke with respect to those in the other group. Consequently, those in one group perform their driving strokes while the others perform their compression strokes and vice-versa.

In either group, all the pistons located on the same side with respect to the median plane located at the inner dead-centre are connected rigidly with one another and with the pistons in the other group located on the opposite side with respect to the dead-centre median plane. Such connection of the pistons may be eiected so as to establish the connection of a piston in a given cylinder at one side of the median plane to a piston of another cylinder, that is, a cylinder of the other group, which is offset with respect to said given cylinder both in the same general direction as and transversely of the general direction of the common central axis about which the cylinders are distributed. By thus connecting the plurality of pistons of the cylinders in such offset arrangement the forces acting on the structure about the common central axis which are developed in the operation of the pistons within their cylinders may be brought into balanced relation While securing the advantage that the pistons thus connected are out of phase with each other by one stroke and a power impulse is secured for each stroke.

Either piston group thus provided may be connected in the conventional manner with a number 0f compressor pistons or may be connected with a number of compressor cylinders, which' cylinders also are movable in the directions of the piston strokes.

A free-piston machine is thus obtained, which may be of either the compressor or the prime mover type, wherein a driving stroke is available at every Stroke and the driving cylinders of aelonove which need not be mounted in tandem, this being an obiect of this invention.

The arrangement described will admit of a great many practical embodiments.

In particular, the arrangement described above by way of example is most valuable in the practical application of the invention disclosed in the applicants French Patent 855,700 and in the corresponding United States application Serial No. 765,454. filed August 1, 1947 which discloses a free-piston and cylinder apparatus devoid of mechanical rod-and-crank connections. It is evident that every element in either movable assembly has a corresponding element in the other assembly geometrically positioned with respect the common central axis so as to be subjected (in the reverse direction) to pressures which are exactly the same at any time.

It is also clear that where particular reasons make it necessary, instead of allowing the median I planes transverse to the central axis of all the lprime movers or motors to coincide as in the above described example, there is no objection to these planes being parallel and stepped, however at the cost of an increase in the length of the machine.

It is also possible with the disposition of cylinders about the central axis to operate tandem prime movers and tandem air compressors, without increasing the length of the machine, by placing the compressor elements side by side with the prime movers instead of being arranged in line.

In Figs. 1 and 2 is shown an arrangement in which each prime mover or compressor element consists of a pair of cylinders open at the ends and arranged end to end, each of these cylinders being provided with two free pistons, the pistons being connected in groups to form two movable assemblies, one of the movable assemblies comprising the sets of outer pistons and the other the sets of inner pistons.

All the pistons in each of said four sets are interconnected by a tie-ring of suitable section, the rings 48 and 49 in the one assembly and the rings 45, 44, 46 in the other assembly having the same horizontal projection. Tie-rings 45 and 49 .are rigidly connected with each other by eight pairs of longitudinal stay-bolts 50, 50', 50", etc., which are secured in lugs proiecting from the upper and lower annular faces of the related tierings; likewise, tie-rings 45, 44, 48 are interconnected by similar staybolts 41, 41', 41",...secured in said tie-rings and projecting with clearance through the tie-rings 48 and 49.

Tie-rings 45 and 48 are provided with babbitted shoes 54 and 55 respectively adapted to bear ona suitable lubricated cylindrical guide 5I.

In the-same way, tie-rings 49 and 46 are provided with similar shoes 56 and 51 adapted to bear on a corresponding guide 52.

It will be appreciated that bv this combination each movable assembly provides a practically rigid unitary whole. Besides, should the state 'of balance be disturbed accidentally, even one leading to a considerable unbalanced stress amounting e. g. to 5.000 kg., the t'lting effect set up v is counteracted by the resistance opposed to such motion by the guides 5| and 52. Since in a full size practical embodiment the lever-arm of the unbalanced force is in the order of one tenth of the lever-arm of the countermoment applied on the shoes of the outer ring-ties of each movable assembly, it will be appreciated that the order of magnitude of the frictional stress on guides 5l consequently is easily taken care of by the Guides.

In the modification shown in Figs. 3 and 4 the connection of the elements providing either movable assembly, instead of being secured by a pair oi cylindrical tie-rod sets, is obtained through the medium of a pair of concentric cylinders Il, l! of suitable diameters.

The connection between the pistons provided in either movable assembly and the corresponding cylinder Il or 52 is obtained by means of suiiiciently resistant and suitably apertured discs or spiders 5l. It will be seen in Fig. 4 that where the disc 53 has a ring-like shape it is unnecessary that the axes of the various associated pistons should be distributed on a circumference, the only condition to be satisfied being that the resultant of the thrusts on all the pistons secured to one and the same disc shall coincide with the axis of the central cylinders Il, 52. This can be obtained e. s. by arranging the elements to be interconnected in pairs 'symmetrically with respect to the center and so that equal thrusts be set up on the symmetric elements of a pair.

With a view to resisting the tilting forces, in the same way as in the embodiment of Figs. l and 2, cylinders BI, I2 may be guided at their outer ends by cylindrical stationary babbltted and lubricated guides not shown in the drawing.

As modifications. various combinations may also be contemplated in which the connection means of both of the above embodiments are combined. For instance, one of the movable assemblies may comprise such a central cylinder as 6l (Figs. 3I and 4). and the other such a tierod system as 41, 41', 41". (Figs. 1 and 2).

Whatever the connecting svstem may be, a most important precaution is to be taken in the 'mounting of the pistons.

expedient to provide for a certain play of the piston with respect to the ring carrying the same. Such result may be attained as shown in Fig. 3.

AIn this modification, instead of bearing directly surfaces.

on the corresponding face of the disc. the piston rests on a cap-shaped stud 54. For that purpose, the piston carries a correspondingly cup-shaped bearing member. Said bearing members can be obtained simply as chill-cast white metal parts. The stud 64 is supported to move through a irac- -tion oi' a millimeter in all directions, whlle the axis of the piston can swing slightly about the geometrical center of the end cap of the stud. Obviously, such displacements have a small amplitude. In principle, they take place only at starting, when the piston takes its set coaxially with the cylinder. However, it is advisable to provide for some lubrication of the co-operating The pistons are kept in engagement with the disc studs by spring fastenings such as 55. 88 (Fig. 3).

It is pointed out as an essential characteristic of this invention that owing to the great number of cylinders and to the fact that they are coupled in pairs in series so that, in fact, they provide double-acting machines, it is possible, by utilizing a number oi driving cylinder groups which is a multiple oi l, to obtain by this method fourcycle tree piston prime movers, a result which has not been obtained up to the present. ln ,this arrangement, although the machines are oil the four-cycle type, the pistons of both cylinders in each pair of diametrically oppositely positioned cylinders are always in phase with each other. lFour-cycle tree-piston motors, especially when supercharged, possess remarkable particular advantages, although they involve a mechanically controlled timing gear.

The support of the machine is provided by conventional means and calls for no special explanation.

Safety in operation is secured essentially by the iact that since the motive elements are associated in pairs in tandem arrangement, those elements which happen to be in the compression phase will act naturally as safety cushions. Moreover, the lengths and clearances are so dehned that in the event oi a shoclr occurring between both movable assemblies said shocir shall taire place in the one case between the outer tie-rings and in the other case between the end discs on the outer tube and the central tube. Under such conditions, the tiarods in the hrst case and the central tubes in the second case will emciently act as yielding springe.

in the design oi high-power groups, two or three units constructed as described hereinbetore can be associated in tandem arrangement one above the other.

ilihat l claim as my invention and desire to secure by Letters Patent is:

l. it iluid pressure machine of the reciprocating type comprising a plurality of sets of cylinders distributed about a common axis with the axes oi the cylinders extending in the same gcn-n eral direction as said common axis and with a given cylinder of each set positioned with respect to another cylinder oi said set oiiset both in said general direction and transversely of said general direction, each cylinder having a piston operable therein in reciprocating relation thereto, and means connecting the piston of said given cylinder oi each set to the piston of the cylinder oi said set which is oflset with respect thereto so that said pistons move concomitantly to decrease and increase the volume in said given cylinder while respectively increasing and decreasing the volume in said other cylinder, the given cylinders oi the sets being in axially aligned relation to the other cylinders oi another set to provide,

tor balancing of the forces acting on the structure about said common axis, said connecting means comprising equalizing means operatively connected to said pistons and cooperating with said connecting means to provide relative displacement between said connecting means and the respective pistons so as to allow ior slight misalignment of said pistons and the cylinders in which they operate.

2. il iluid pressure machine of the reciprocating type comprising a. plurality of sets of cylinders distributed about a common axis with the axes of the cylinders extending in the same general direction as said common axis and with a given cylinder oi" each set positioned with rcspect to another cylinder of-said set odset both in said general direction and transversely of said general direction, each cylinder having a piston operable therein in reciprocating relation there to, and means connecting the piston of said given cylinder oi each set to the piston of the cylindmr oi said set which is odset with respect thereto so that said pistons move concomitantly to decrease and increase the volume in said given cylinder while respectively increasing and decreasing the volume in said other cylinder, the given cylinders of the sets being in axially aligned relation to the other cylinders of another set to provide for balancing of the forces acting on the structure about said common axis, said means connecting the piston of the given cylinder oi each set to the piston of the cylinder of said set which is oiiset with respect thereto comprising a plurality ci.' concentric cylinders coaxial with said common axis about which said plu rality of sets of cylinders are distributed and respectively connected to said sets of pistons for axial movement of said concentric cylinders relative to each other together with the respective sets of pistons, said sets of cylinders being distributed about said axis exteriorly of said concentric cylinders.

3. iii iluid pressure machine of the reciprocat ing type comprising a plurality of sets of cylinders distributed about a common axis with the axes oi the cylinders extending in the same general direction as said common axis and with a given cylinder of each set positioned with respect to another cylinder oi said set oftest both in said general direction and transversely of said general direction, each cylinder having a piston operable therein in reciprocating relation thereto, and means connecting the piston of said given cylinder oi each set to the piston of the cylinder of said set which is odset with respect thereto so that said pistons move concomitantly to decrease and increase the volume in said given cylinder while respectively increasing and decreasing the volume in said other cylinder, the given cylinders oi the sets being in axially aligned relation to the other cylinders of another set to provide for balancing oi the forces acting on the structure about said common axis, said means connecting the piston of the given cylinder of each set to the piston oi the cylinder of said set which is odset with respect thereto comprising a pair of concentric cylinders coaxial with said common axis about which said plurality of sets of cylinders are distributed, said sets of cylinders being distributed about said axis exteriorly of said concentric cylinders, and means for guiding said concentric cylinders for axial movement thereof relative to each other, said concentric cylinders respectively being connected to said sets of pistons to produce said relative axial movement concomitantly with reciprocating movement of said pistons in their respective cylinders.

d. A fluid pressure machine of the reciprocating type comprising a plurality of sets of cylinders distributed about a common axis with the axes of the cylinders extending in the same general direction as said common axis and with a given cylinder of each set positioned with respect to another cylinder of said set oiset both in said general direction and transversely of said general direction, each cylinder having a piston operable therein in reciprocating relation thereto, and means connecting the piston of said given cylinder of each set to the piston of the cylinder of said set which is odset with respect thereto so that said pistons move concomitantly to decrease and increase the volume in said given cylinder while respectively increasing and decreasing the volume in said other cylinder, the given cylinders of the sets being in axially aligned relation to the other cylinders of another set to provide for balancing of the forces acting on the structure about Asaicl common axis, said means connecting the piston of the given cylinder of each set to the piston of the cylinder of said set which is offset with respect thereto comprising a pair of concentric cylinders coaxial with said common axis about which said plurality of sets of cylinders are distributed, said sets of cylinders being distributed about said axis exteriorly o said concentric cylinders, and equalizing means opera tively connected to said pistons and to the respective concentric cylinders to provide relative motion therebetween so as to allow for slight misalignment of said pistons and the cylinders in which they operate.

5. A iiuid pressure machine of the reciprocating type comprising a plurality of sets of cylinders distributed about a common axis with the axes of the cylinders extending in the same general directionas said common axis and with a given cylinder of each set positioned with respect to another cylinder of said set offset both in said general direction and transversely of said general direction, each cylinder having a piston operable therein in reciprocating relation thereto. means connecting the piston of said given cylinder of each set to the piston of the cylinder of said set which is offset with respect thereto so that said pistons move concomitantly to decrease and increase the volume in said given cylinder While respectively increasing and decreasing the volume in said other cylinder, the given cylinders of the sets being in axially aligned relation to the other cylinders of another set to provide for balancing of the forces acting on the structure about said common axis, said means connecting the piston of the given cylinder of each set to the piston of the cylinder of the set which is offset with respect thereto comprising a plurality of members extending about said common axis about which said plurality of sets of cylinders are distributed, means respectively connecting said members to said sets of pistons for axial movement of said members relative to each other together with the respective pistons, and means cooperating with said members for guiding said members for said axial movement thereof relative to each other, said sets of cylinders being distributed about said common axis exteriorly of said connecting means.

6. A uid pressure machine of the reciprocating type comprising a plurality of pairs of cylinders distributed about a common axis with the axes of the cylinders extending in the same general direction assaid common axis and with a given cylinder of each pair spaced with respect to the other cylinder of said pair in said general direction, each cylinder having a pair of pistons therein oppositely reciprocatable in said general direction, means connecting the adjacently distogether in 'the reciprocating movement thereof in the respective cylinders, a member connecting together said connected adjacent pistons of the pair of cylinders to form a unit reciprocatable in said general direction upon reciprocation of the respective adjacent pistons in their respective cylinders, means connecting the outwardly disposed pistons of each pair to move together in the reciprocating movement thereof in their respective cylinders, a second member connecting said connected outwardly disposed pistons of said pairs of cylinders to form a unit reciprocatable in said general direction upon reciprocation of said outwardly disposed pistons in their respective cylinders, and means cooperating with said members for guiding said members for said movement thereof in said general direction relative to each other, said pairs of cylinders being distributed about said common axis generally exteriorly of said guiding means.

7. A fluid pressure machine as dened in claim 6 which comprises equalizing means supported by said members and operatively connected to said pistons to provide relative displacement between said members and said pistons in a plurality of directions laterally of the movement thereof in their cylinders so as to allow for slight misalignment of said pistons and the cylinders in which they operate.

8. A iiuid pressure machine as defined in claim 7 in which said equalizing means comprises bearing elements carried by the respective members for displacement of said bearing elements relative thereto laterally of the movement thereof, said bearing elements being adapted for pivotal engagement of the respective pistons therewith which are connected to the respective members, and yielding elements connecting said members and the respective pistons'to provide for such lateral and pivotal movements of said bearing elements and pistons.

ERNEST MERCIER.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,168,877 Froelich Jan. 18, 1916 1,223,701 Krinitz Apr. 24, 1917 1,545,517 Powell July 14, 1925 1,829,631 Burhop Oct. 27, 1931 1,987,699 Moore Jan. 15, 1935 2,083,680 Anderson et al June 15, 1937 2,147,186 Alfaro Feb. 14, 1939 2,306,978 Pateras-Pescara Dec. 29, 1942 

